Getter device and method of use

ABSTRACT

A getter assembly having a getter container and an annular support.

Zucchinelli States atent 1191 5] Dec. 23, 1975 GETTER DEVICE AND METHOD OF USE [75] Inventor: Mario Zucchinelli, Milan, Italy [73] Assignee: S.A.E.S. Getters S.p.A., Milan, Italy 22 Filed: May 15, 1974 I [21] Appl. No.: 470,183

[30] Foreign Application Priority Data May 18, 1973 Italy 24291/73 [52] US. Cl 417/48; 316/25 [51] Int. Cl. F04B 37/02 [58] Field of Search 417/48; 313/174; 316/25 [56] References Cited UNITED STATES PATENTS 3,381,805 5/1968 Porta 417/48 3,669,567 6/1972 Porta 417/48 3,719,433 3/1973 Rabusin 417/48 3,768,884 10/1973 Porta 316/25 Primary Examiner--William L. Freeh Assistant Examiner-G. P. LaPointe Attorney, Agent, or Firm-Littlepage, Quaintance, Murphy & Dobyns [57] ABSTRACT A getter assembly having a getter container and an annular support.

2 Claims, 3 Drawing Figures US. atent Dec. 23, 1975 GE'I'IER DEVICE AND METHOD OF USE FIELD OF THE INVENTION The present invention relates to getter devices used in kinescopes which have critical electron gun alignment characteristics and which are also susceptible to damage by heat, especially the heat produced in the getter device during evaporation of getter metal vapors.

BACKGROUND OF THE INVENTION The use of getter materials in the manufacture of electronic tubes is well known. A commonly used getter device construction consists of a U-shaped channel getter material container in annular form with a getter material contained within the channel. This assembly is mounted within an electron tube, for example a color television picture tube. After the tube is evacuated, the residual gases left in the tube are removed by heating the getter container and material contained therein to a high temperature, suitably by induction heating, whereupon the getter material is flashed or vaporized. The vaporized getter material adsorbs or reacts with the residual gases and removes them as low vapor pressure solid condensates and continues to adsorb any further liberated gases throughout the life of the tube.

Usually the getter material principally comprises: a mixture or alloy of metals such as, for example, barium and aluminum. It is the barium component of this mixture which provides the reactive material. The clean up of residual gases in television picture tubes, and particularly color tubes, requires a relatively large amount of active barium material. For example, 25 inch screen color tubes having three electron guns and a metal shadow mask have been found to require a yield of 175 to 225 mg of barium. Since the barium-aluminum powder mixture might have contained up to about 50 percent aluminum, the total amount of gettering powder mixture in the container before flashing could be from 350 to 450 mg. It has further been found desirable to employ exothermic gettering powders in color television picture tubes. An exothermic gettering powder can comprise: a barium-aluminum alloy or mixture plus about an equal weight of powdered nickel. The nickel reacts exothermically with the aluminum upon heating to supply additional heat for evaporating the barium. The self-generated heat lessens the getter flashing time from say 30 seconds for an endothermic type getter to about 15 or 20 seconds with the exothermic type getter.

A typical channel ring exothermic getter used in color television picture tubes thus may contain, for example, 1000 mg of a 25 percent barium-25 percent aluminum-50 percent nickel exothermic alloys yielding about 200 mg of barium on heating. The getter container itself may comprise a U-shaped channel formed into a ring of, for example, about 2.54 cm outside diameter and having a channel width of say 0.5 cm. Altemafively the outer diameter may be about 2 cm and the channel width may be about 0.5 cm. The getter powder is pressed into the channel. The flashing of the getter requires heating to a high temperature, about l300C, to vaporize the barium, or whatever getter material is utilized. As a result of this heating, the residue and the channel ring container are themselves heated to a high temperature. This heating results in the melting or sintering of the residue, either the aluminum powder in an endothermic getter, the barium-nickel-aluminum powder in the case of the exothermic alloy described above, or whatever unflashed material is present. The container itself, generally stainless steel, is itself heated to a temperature often near its melting point; and in the case of improperly formed or positioned getter assemblies, the stainless steel ring may melt.

The presence of this extremely hot getter container in a glass-walled electron tube can cause serious problems as will be seen from the following: an electron tube, particularly a television picture tube generally comprises a neck portion in which are located the electron gun or guns and auxiliary equipment; an enlarged bulb portion which terminates in a generally flat viewing screen; and a funnel-shaped portion joining the neck and bulb portions. Whereas in the past, the ring shaped getter container was usually mounted in the neck portion of the tube positioned on the electron gun, it is now a desired practice to mount the getter container in or near the funnel portion of the tube. Since the getter container must be outside the path of the stream of electrons directed from the electron gun toward the screen and since the diameter of the funnel cross-section at the selected site may be only slightly larger than that of the neck portion, it is necessary to have the getter container actually abutting against the wall of the tube. This is accomplished by mounting the getter container at the end of a spring-like metallic strip support or antenna, the other end of which is fixed to a wall of the elecu'on gun in the neck portion of the tube. The spring is biased to force the getter container against the wall of the tube in the funnel portion and thus keep clear the path for the electron beam.

This positioning of the getter container in direct contact with the glass walls of the tube can and often does cause cracking of the glass when the getter container is heated inductively to high temperatures during flashing. Since the television tube is for the most part completely fabricated just prior to gettering, the cracking of the tube at this time is a substantial loss. In addition it is important that the getter container be properly aligned inside the tube so that the gettering flash is properly directed. Such alignment is difficult to achieve using normal production line techniques.

Getter devices having high barium yields and providing protection against thermal breakage of television picture tubes have been described in US. Pat. No. 3,390,758 assigned to Union Carbide Corporation and US. 'Pat. No. 3,381,805 assigned to SAES Getters S.p.A. The means of protection against thermal breakage of the television picture tube or kinescope was by means of the provision on the getter device of a ceramic support material having a low thermal conductivity and being opague to thermal radiation.

Unfortunately these devices even when having a central core opening are very heavy and in consequence the spring or antenna which is used to hold the getter device in position on the wall of the kinescope has to be tron beam gun structure causing it to be deviated or I misaligned from its intended position which, in the case of color television kinescopes causes a misalignment of the electron beam with respect to the shadow mask and phosphor spots such that an inferior picture is produced. This is also true when the electron beam must be accurately oriented in other types of kinescopes such as those required for precision radar, storage tubes and computer output displays among others.

A counter balancing antenna spring or other means mounted on the opposite side of the electron gun can not be used to overcome these difficulties as the combined forces of the antenna spring and counter balancing means would exert such a high combined total force as to distort the dimensions of the accurately designed electron gun. Such distortions lead to imperfect functioning of the tube. 7

Furthermore, prior getter devices with annular ceramic bases have had an annulus that was open through the device. See FIGS. la, 1b, 3a and 3b of US. Pat. No. 3,381,805 and FIGS. 7, 8, and 14 of US. Pat. No. 3,390,758. Getter metal can pass through this annulus and be deposited on the glass surface of the kinescope during exposure to induction heating. This undesirable deposit can also pick up induced currents causing further undesirable localized heating of the glass.

It is therefore an object of the present invention to provide an improved getter assembly free from one or more of the defects of previous getter assemblies.

A further object of the present invention is to provide a getter device with a support of annular shape.

Another object is to provide a getter device of minimum weight while still having the advantages of previously known getter assemblies.

Still another object is to provide a getter device which precludes the deposition of getter metal on the walls of the kinescope directly underneath the device.

Yet another object of the present invention is to provide a getter assembly which does not substantially afiect the electron gun alignment.

Further objects and advantages will be recognized by one skilled in the art by reference to the following drawings and description wherein:

FIG. 1 is a cross sectional view of a getter device of the present invention,

FIG. 2 is a cross sectional view of an alternative getter device of the present invention,

FIG. 3 is a representative cross sectional view of color kinescope using an antenna mounted getter assembly.

FIG. 1 shows a getter assembly of the present invention. Getter assembly 10 comprises a channel getter material container 11 having outerside wall 12 and an innerside wall 13. Inner and outer side walls are connected at spaced intervals by bottom connecting elements, not shown, which may be integral with the wall material. Getter metal vapor releasing material 14 is placed within container 11. The getter material may also contain a gas releasing material as described in US. Pat. No. 3,389,288. The outer radius r., of support 16 is substantially equal to the outer radius r;, of container 11. If the inner radius r of support 16 is substantially less than the inner radius r of container inner wall 13, then the mass of the getter assembly 10 is increased to too high a value. Preferably radius r should be greater than r Ideally r r r and r r,,. A gas releasing device 17, as described in US. Pat. No. 3,669,567 may be attached to coupling element either on the side of the coupling element holding the support 16, as shown, or alternatively it may be placed 4 on the side of the coupling element to which container 11 is attached. It is preferably placed on the axis 18 of the assembly 10.

In spite of the fact that the hotter parts of the coupling element 15, heated during getter flash by the getter vapors at about 1,000C or more, are now exposed to the glass walls of the kinescope they do not cause the kinescope to break, and the mass of the getter assembly has been substantially reduced.

Support 16 has a stepped structure giving two lower curved surfaces 19, 19 to give at least two point lines of contact during insertion of the getter assembly into the kinescope reducing localized pressure of contact between the kinescope and getter device. This reduces danger of loose particles from internal coatings.

FIG. 2 shows another preferred getter assembly 20 identical in all respects to the getter assembly of FIG. 1 except that the support 21 has a concave inner surface 22 and a convex outer surface 23 thus providing a further reduction in total mass but at the expense of robustness.

FIG. 3 shows a getter assembly 31, in a kinescope 30, attached to one end of an antenna spring 32 whose other end is attached to an electron gun 33. Electron gun 33 is located in a fixed position relative to the axis 34 of kinescope 30, usually by means of three positioning springs 35 (only one shown). An electron beam 36 from gun 33 passes through a hole 37 of a shadow mask 38 and strikes a portion of phosphor 39 on the face plate 40 of kinescope 30. A slight displacement of electron gun 33, due to excessive pressure of the getter assembly 31, relative to axis 34 causes the electron beam 36 to be displaced away from shadow mask hole 37 with consequent failure to properly excite phosphor 39. A getter assembly of the present invention does not cause this defect as antenna 32 does not have to be heavily pretensioned.

EXAMPLE A U-shaped channel container having opposite side walls and distanced bottom connecting elements is filled with 1 gram of a mixture of nickel and approximately 50 percent Ba 50 percent Al alloy in the ratio of about 1:1 to which a small percentage of iron nitride has been added. The getter material containing container is spot welded to a disc-shaped coupling element as shown in FIG. 1. A second gas releasing material is placed in a small metal container and attached to the center of the coupling element to which is then attached an annular ceramic support of cross section shown in FIG. 1. The assembly is attached to one end of an antenna spring the other end of which is then attached to the electron gun of a color television kinescope. The gun-getter assembly combination is inserted in the kinescope which is then, baked, pumped and otherwise treated in the normal manner, whereupon thekinescope is sealed. The getter'device is caused to release barium vapor by high frequency induction heating. The kinescope does not break.

On operating the kinescope to produce a colored image it is seen that the electron gun is in the desired alignment and not displaced from its desired position by too high a getter assembly-kinescope-wall pressure.

The kinescope presents a low amount of barium on the used in the specification and claims herein is meant to erable detail with reference to certain preferred embodiments designed to teach those skilled in the art how best to practice the invention, it will be realized that other modifications may be employed without departing from the spirit and scope of the appended claims.

What is claimed is:

1. A getter assembly comprising:

A. an annular container,

B. a getter metal vapor releasing material within the container,

C. an annular support attached to the bottom of the container, said annular support having an inner radius and an outer radius 1. said annular support being of a material of low thermal conductivity, 2. said annular support being of a material of high resistance to heating by induction currents,

3. wherein the inner radius of the annular support is greater than the inner radius of the annular container,

4. wherein the outer radius of the annular support is substantially equal to the outer radius of the annular container.

2. A getter assembly adapted to be subjected to induction heating currents while said assembly is within an evacuated kinescope and resting on the wall of the kinescope without transmitting a damaging amount of heat to said walls of said kinescope and without substantially disturbing the kinescope electron gun alignment, comprising:

A. A channel container having an inner side wall, an outer side wall and a bottom connecting the inner side wall with the outer side wall,

B. a getter material within said container, in admixture with a nitrogen gas releasing material,

C. an annular shaped support, made of a material of low thermal conductivity and of high resistance to heating by induction current, wherein the diameter of the central core opening extending through the support is greater than the diameter of the inner side wall of said container,

D. a disc shaped coupling element joining said annular shaped support and said channel container and,

E. a second nitrogen gas releasing material attached to the coupling element remote from the getter material. 

1. A getter assembly comprising: A. an annular container, B. a getter metal vapor releasing material within the container, C. an annular support attached to the bottom of the container, said annular support having an inner radius and an outer radius 1 said annular support being of a material of low thermal conductivity, 2 said annular support being of a material of high resistance to heating by induction currents, 3 wherein the inner radIus of the annular support is greater than the inner radius of the annular container, 4 wherein the outer radius of the annular support is substantially equal to the outer radius of the annular container.
 2. A getter assembly adapted to be subjected to induction heating currents while said assembly is within an evacuated kinescope and resting on the wall of the kinescope without transmitting a damaging amount of heat to said walls of said kinescope and without substantially disturbing the kinescope electron gun alignment, comprising: A. A channel container having an inner side wall, an outer side wall and a bottom connecting the inner side wall with the outer side wall, B. a getter material within said container, in admixture with a nitrogen gas releasing material, C. an annular shaped support, made of a material of low thermal conductivity and of high resistance to heating by induction current, wherein the diameter of the central core opening extending through the support is greater than the diameter of the inner side wall of said container, D. a disc shaped coupling element joining said annular shaped support and said channel container and, E. a second nitrogen gas releasing material attached to the coupling element remote from the getter material. 